Is Case structure what I need (newbie)

[dkl234]

I'm attempting to write a VI to control a multi zone furnace. The board(s) used to control the furnace take about 25 different commands.

I'll be sending commands (strings) over a serial port. Commands take differing arguments so there are variable inputs for concatenating

a string into a valid command before writing to the serial port. Further complicating things, each string includes a checksum at the end.

Currently users are expecting to select a command (in simple english, not what is sent over the port) and provide added info based on

the command. I then gather this up, format a string that the board understands and write it to the port.

I'm guessing the Case structure is what I should be using. But as far I can tell (I'm a newbie so I can't sure of much), for each case in the

structure it appears that the inputs to the concatenation have to be the same in type, order and number. I keep getting errors if I attempt

to use a Case structure where one case uses 2 strings to concatenate into a command, another uses 5 strings etc. I get unwired element

errors.

Is the Case structure limited in the way I'm seeing or is there a way around this (something a newbie doesn't know)?

Or is there a different structure I should be using?

I've attached 2 VIs (both are just baby steps at this point, the "bad" is expecting more strings than there are).

Any advice would really help.

Thanks,

Dave

[crossrulz]

Since you are just concatinating strings, just output empty strings out of those cases that shouldn't have that input.

[aputman]

.... Or move the concatenate function inside the case structure.

[dkl234]

Thanks crossrulz, aputman,

I'll try both ways and see how things go. It's a pain in the neck being a newbie!

[billko]

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@dkl234 wrote:

Thanks crossrulz, aputman,

I'll try both ways and see how things go. It's a pain in the neck being a newbie!

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But you have the right attitude and that makes all the difference in the world!

[crossrulz]

We were all newbies at one point.  Just keep asking questions and learn from our mistakes.

[Eric1977]

I think a State Machine with an Event Structure is right up your alley for this project. 😉

[dkl234]

Eric

You might be right. I'm at the start of the learning curve on labview. One thing is for certain, I don't know enough about labview

to know when I might be going down the wrong road. So in the mean time it's a number of mini vis until I can see the light

on the overall project. 

[Dennis_Knutson]

Another option is a formal instrument driver. You can use the Create Instrument Driver wizard to generate a basic template and then start customizing. You can look at existing examples by browsing http://www.ni.com/downloads/instrument-drivers/

[Eric1977]

I use the loaded templete examples as a good starting point and go from there. You can always come here if you get stuck. I do.